I4C NetD Mdhod ofextraSing Silver from 



method, the requifite or precife proportion of lead to copper, was totally unknown. As in- 

 genious, however, as the modern eliquating procefs may appear in a chemical view, it is 

 ftill in its own nature attended with many confiderable imperfedtions; namely, a great lofs 

 of time, of fuel, and efpecially of lead. Thefe imperfeftions are infeparable from this 

 procefs, and render it fo very expenfive, as to be totally inapplicabla in the operations with 

 black copper*, which contains lefs than four ounces of filver. It is well known that Barn 

 has recommended the amalgamation of the copper-mat as a more advantageous method to 

 cxtradl its filver. But even though the amalgamating procefs, of which the efficacy and 

 utility is manifeft in the richer filver ores, had not been proved by experienca to be totally 

 impra£ticable with refpeft to fuch produ£ts as contain lefs filver, for example the copper- 

 mat ; yet the operation is rendered precarious, and its eftablifliment becomes an objedt of 

 rifque from the circumftance, that the material requifite, is in the hands of a pofleflbr, 

 who may raife its price at his own arbitrary choice. 



My refearches into the copper-mat, and its conftituent parts, as well as a more accurate 

 aetiology of the whole of the ufual procefs, of extrafling from it the copper and filver in a 

 feparate ftatc ; together with the inquiries into the mutual powers of chemical attradion 

 of the fulphur and the metals contained in it, have fuggefted to me a new and profitable 

 method of feparating the filver from copper-mat by means of lead, by which the whole 

 procefs of eliquating the black copper is rendered unneceflary. In this method, not only 

 the lofs of lead by oxidation, which renders the eliquating procefs fo expenfive, but like- 

 wife all the other charges of this procefs are avoided ; as for inftance, thofe of the building, 

 and the requifite furnaces and edifices, the neceflary fuel, &c. My method is no lefs Am- 

 ple than eafy ; it is certain and effedlual ; and (what principally recommends it) it requires 

 r^o particular edifice ; but only a flight alteration in the form of the ufual furnace with a 

 concave floor (-^r«M/«i9/^«). It is founded on invariable chemical, hydroftatic principles ; 

 and is found to be praftically applicable and efi"eQual in all the experiments which I have 

 repeatedly made in the fmall way, and which, in this cafe, cannot but be the fame as thofe 

 in the large way. 



Principles, on which the tieiv Adethod is grounded' 



1. Copper-mat confifts of fulphur, copper, iron, and filver ; fo that thefe metals arc, 

 completely diflolved by the fulphur. 



2. Sulphur can diflblve in fufion only a determinate quantity of reguline metals previous 

 to its^faturation. 



3. Sulphur has a ftronger chemical attra£lion for z>o«, than for copper, lead, and filver. 



4. Sulphur like wife attracts «//<•>- more ftrongly, than lead and filver. 



5. And laftly, the chemical affinity of fulphur with lead is greater, than its affinity with 



» . Bla(\ copper is the metal, which is obtained by a fecond fufion from copper or«s.— Tranfl. 



3 filver. 



